1. Field of the Invention
The present invention relates to shaving units having a plurality of cutting edges for use in a safety razor. More particularly, the present invention relates to safety razor shaving units having a plurality of double cutting edge members bonded together.
2. Description of the Prior Art
Double edge safety razors are well-known in the art, and are in many forms. For example, U.S. Pat. Nos. 3,293,745, 3,466,746 and 3,708,879 disclose a razor having sectional caps, an adjustable razor and a razor having a hinged cap, respectively. Such razors act to clamp a thin, flexible double edge razor blade in the razor head with each cutting edge oriented with respect to a guard bar surface.
U.K. Pat. No. 772,532 discloses a shaving unit having two double edge razor blades which are vertically separated by a flexible spacer. The cutting edges of the top blade are set back a slight distance from the cutting edges of the bottom blade to provide tandemly arranged cutting edges on each side of the shaving unit.
U.K. Pat. No. 772,532 contemplates welding the blades and spacer together, and, at Page 3, lines 98-100, specifically teaches welding the spacer near its elongated ends.
Commercially available flexible steel double edge razor blades having an elongated central slot parallel to the cutting edges are arcuately flexed at tab portions at each end of the slot when firmly seated in double edge razors having manually operated mechanisms for opening and closing the cap portion. However, as shown in FIG. 4 of U.S. Pat. No. 3,708,879, the portions of the razor blades between the slot and the cutting edges are at least substantially flat.
Welding metal increases grain size of the metal about the weld, and the corrosion rate about the weld is high. When double edge razor blades are welded together at the tab portions, and the tab portions are thereafter arcuately bent in a razor as specifically taught in U.K. Pat. No. 772,532, a danger of stress-corrosion cracking is raised. Stress-corrosion cracking is failure by cracking under combined corrosion and applied and/or residual stress.